The invention relates to a belt retractor for a vehicle safety belt and a method for actuating a belt retractor.
Known belt retractors comprise a belt spool, at least one locking member which at least largely prevents a belt spool rotation in the case of restraint, and a force limiter which opposes a defined force to a rotation of the belt spool on unwinding. Force limiters (e.g. torsion rods, band extraction devices or deformable threads) are intended to limit the restraining force exerted onto the occupant via the safety belt in an accident. However, the limiting of the force is also disadvantageous in particular situations. For example, extremely heavy occupants can experience a restraining force which is too small through the force limiter which is designed too weak for them. Furthermore, the force limiters are generally coordinated with the gas bag which is additionally present in the vehicle, i.e the two safety systems only develop the optimum restraining effect together. If the gas bag is deactivated, then the restraining effect of the safety belt can be too small. This deactivation of the gas bag is possible for example in the USA on request. Furthermore, a gas bag is of course also deactivated after it has been triggered. After a so-called primary impact, it is therefore no longer available to support the safety belt system. Furthermore, after a primary impact the force limiter is partially destroyed, because force limiters usually consist of plastically deformable elements. Therefore, a smaller restraining effect is available after the primary impact for a second restraint, although a higher restraining effect should be present, because the gas bag is out of operation.
The invention provides a belt retractor which eliminates the above-mentioned disadvantages. The belt retractor according to the invention comprises a belt spool, at least one locking member which at least largely prevents a belt spool rotation in the case of restraint, and a force limiter which opposes a defined force to the rotation of the belt spool on unwinding. Further, a blocking mechanism and an adjusting element for the blocking mechanism are provided. The blocking mechanism can be moved by the adjusting element toward or into a blocking position. In the blocking position, the force limiter is deactivated. This means that the force limiter is bridged with respect to the path of the flux of force and an immediate locking of the belt spool is achieved without the detour via the force limiter. The force limiter, although being bridged, does not have to be completely excluded from the path of the flux of force. Rather, it is also possible for two paths of flux of force to be present in the locking position: a direct one from the belt spool to a blocking member without intercalation of a force limiter, and an indirect one via the force limiter. The term xe2x80x9cat least partially toward another positionxe2x80x9d which is also frequently used hereinbelow means that the adjusting element actuates the blocking mechanism to such an extent that it is brought into the blocking position in a belt webbing-sensitive or vehicle-sensitive manner in the case of restraint. However, this technical expression is also intended to cover the fact that the adjusting element brings the blocking mechanism directly into the blocking position, which can also be a switching under load if, in fact, for example after a primary impact, after a force limiter has acted, the blocking mechanism is moved immediately into the blocking position for the complete locking of the belt spool.
Preferably, in addition the blocking mechanism has a release position in which it does not influence the belt spool rotation. The force limiter therefore acts in this position. If several force limiters are provided, in the release position for example all force limiters can be connected.
According to a development, several force limiters are provided. The blocking mechanism has a further position in which it connects a force limiter. This means that at least three different restraining forces can be achieved. The highest restraining force is provided in the blocking position, a further restraining force on connecting the force limiter becoming active in the further position, and finally a third restraining force when the blocking mechanism is neither in the blocking position nor in the further position (i.e. for example in the release position), so that here only the deactivatable force limiter is in action.
According to the preferred embodiment, the adjusting element is designed such that after a primary impact it brings the blocking mechanism at least partially toward the blocking position. This offers a good restraining effect both in the case of a secondary forward movement of the occupant and also in the case of a subsequent impact (multiple collision or second accident after primary impact).
The position of the blocking mechanism depends on at least one of the following factors:
weight of the occupant,
height of the occupant,
severity of the accident or
position of the occupant in the vehicle.
The latter point should make the so-called out-off-position situation controllable, when the occupant in fact is not sitting centrally and leaning back in the vehicle, but rather has moved from this ideal position before the accident.
According to a development, the adjusting element can be moved manually by an operator and the blocking mechanism can thereby be brought at least partially toward the blocking position. Preferably, the adjusting element here is an adjusting screw. This has the purpose of likewise deactivating the force limiter, e.g. with a deactivated gas bag, so that it can provide a higher restraining force. Also, if for example a very heavy person continually uses the vehicle, the force limiter can be deactivated.
The adjusting element can also be an electric adjusting element, such as a switch for example. This electric adjusting element can be connected with a switch, with a sensor arrangement or for example also with the gas bag control, so that automatically on deactivation of the gas bag, the blocking mechanism is also brought toward the blocking position.
Furthermore, it is also possible to achieve an automatic movement of the adjusting element in a purely mechanical manner. Here, the adjusting element is coupled mechanically with the belt spool. In the case of restraint, when belt webbing is unwound under load, the belt spool rotation leads to such a movement of the adjusting element that the blocking mechanism is shortly before the blocking position. This can be achieved for example in that the adjusting element is a clutch disc which on acceleration in the case of restraint moves a control catch as blocking mechanism toward the blocking position. Furthermore, it is also possible in the case of restraint to couple the belt spool with a nut/spindle arrangement, whereby the spindle is set into rotation and the nut, which is not co-rotating, is displaced axially. The nut can then serve as adjusting element. A further possibility for mechanical coupling consists for example in the provision of an oblique plane or a crank which in the case of restraint are set in rotation, in order to divert an adjusting movement.
Furthermore, the adjusting element can also be constructed as a pyrotechnical adjusting drive. The blocking mechanism preferably comprises a blocking member in the form of a displaceable locking catch. The locking catch engages in the locking position into a locking toothing associated with the belt spool, hereinafter named the belt spool locking toothing. If several force limiters are provided, the blocking mechanism has a further position, in which it connects a force limiter. In each case the force limiters have a separate locking toothing associated with them. The displaceable locking catch engages in the further position into a locking toothing of a further force limiter. Thereby, this force limiter is connected for example when a heavy occupant is present or if there is a serious accident.
A band extraction device or a torsion rod for example come into consideration as force limiters. Each force limiter can have its own locking toothing associated with it and its own locking catch or the displaceable locking catch.
The present invention relates in addition to a method for actuating a belt retractor comprising a belt spool, at least one locking member which at least largely prevents a belt spool rotation in the case of restraint, a force limiter which opposes a defined force to a rotation of the belt spool on unwinding of said safety belt, a blocking mechanism, an adjusting element for the blocking mechanism and comprising several force limiters, the adjusting element being designed such that, by actuation of the adjusting element after a primary impact, an other force limiter is force transmitting.
According to a further method the force limiter is deactivated by actuating the blocking arrangement after a primary impact. If several force limiters are present, then all of them are deactivated. As the force limiter acting during the primary impact is usually plastically deformed, a restraining effect can again be achieved by the belt retractor, e.g. for a secondary impact. The idea of bringing an other limiter in a force transmitting path is not limited to a retractor having force limiters of which can be deactivated.